1. Field of the Invention
This invention relates in general to subsea well assemblies, and in particular to a connector for connecting a high pressure wellhead housing into a low pressure wellhead housing.
2. Description of the Prior Art
In one type of offshore well drilling, a low pressure wellhead housing will be installed on the sea floor. The low pressure wellhead housing is a large tubular member, having conductor pipe that extends into an initial portion of the well.
A high pressure wellhead housing lands in and secures to the low pressure wellhead housing. The high pressure wellhead housing is a tubular member with casing located on the lower end that extends to a deeper depth in the well than the conductor pipe. A string of riser will connect the high pressure wellhead housing to surface drilling or production equipment.
Waves and currents will cause a bending force on the string of riser. This force transmits down to the high pressure wellhead housing. If the high pressure is allowed to move back and forth, this rocking action can eventually fatigue the metal. The point where the high pressure wellhead housing connects to the casing will normally experience the greatest fatigue and may result in a failure.
There are various proposals for tightly locking the high pressure housing to the low pressure housing so as to prevent relative rocking movement between the high pressure wellhead housing and the low pressure wellhead housing. If the high pressure housing is not movable relative to the low pressure housing, the strength of the low pressure housing will assist in preventing rocking movement of the high pressure housing, thereby reducing fatigue. These proposals generally involve wedge members which tightly wedge the high pressure housing into the low pressure housing.
Also, the high pressure housing will be latched by a connector into the low pressure housing so as to prevent any upward force due to loads from the riser or blowout preventer stack. These latch connection members also will fatigue due to bending forces of the riser.